We update the estimates of the growth and length-weight parameters for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea region (Subareas 88.1 and SSRUs 88.2AB). We present revised estimates of the von Bertalanffy growth curves, estimates of mean length at age using maximum likelihood estimation (MLE), and the length-weight relationship based on available CCAMLR SISO data collected from fishing operations in the Ross Sea region.
Estimates of growth and length-weight were similar to those previously used, however there was some suggestion that the shape of the growth curve may be better approximated by the MLE mean length at age relationship rather than by the von Bertalanffy equation. Stock assessment model estimates of B0 and 2017 spawning stock biomass (B2017) and stock status (%SSB2017) were lower than with the previous von Bertalanffy relationship. But estimates of %SSB2017 were very similar between the revised von Bertalanffy and the MLE mean length at age model. In this case, the model conclusions were very similar and either of the updated relationships may be adequate parameterisations in the Ross Sea region stock assessment model.
Investigation of residual patterns in the fits to the relationships showed no evidence of systematic change in these parameters over time.